1. Field of the Invention
The present invention relates to a secondary battery, and more particularly, to an electrode assembly for a secondary battery in which the welding characteristics of the collector plate against the electrode plate are improved, and a method of manufacturing the same.
2. Description of the Related Art
Unlike a primary battery, a secondary battery may be recharged.
A low power secondary battery, in which one battery cell is made into a battery pack, is used as a power source for various portable electronic devices such as cellular phones, laptop computers, and camcorders. The high power secondary battery in which several to tens of battery cells are made into a battery pack is used as the power source for motor driven devices such as hybrid electric vehicles.
Depending on the external shape, secondary batteries may be classified into different types, for example, square and cylindrical batteries.
The secondary battery includes an electrode assembly in which positive and negative electrodes of a belt shape are wound with a separator interposed therebetween. The electrode assembly is placed inside a container, and a cap assembly having an external terminal is mounted in the container.
Conductive taps are attached to the positive and negative electrodes, respectively, to collect electric current generated from the electrode assembly to the cap assembly or the container. The taps are fixed to the positive and negative electrodes by welding, etc.
A bulk size secondary battery requiring high power has a collector plate of a plate shape for the taps, such as that disclosed in U.S. Pat. No. 6,193,765.
However, in a secondary battery having the collector plate, when the collector plate is electrically connected to the electrode assembly, there is a problem that the probability of damaging the connection is high.
Generally, the collector plate is connected to an uncoated region, a portion which is uncoated with active material on the collector of the positive and negative electrodes, by welding. However, when the collector plate and the uncoated region contact each other, the uncoated region is easily bent by the force of the collector plate. This bending direction may be non-uniform, and accordingly, the uncoated region does not properly contact the collector plate.
Therefore, the contact between the collector plate and the uncoated region is poor, and moreover, the welding between these two elements is not properly carried out.
When such a problem occurs in a bulk size secondary battery requiring high power, such as hybrid electric vehicle, not only the secondary battery but also the device using the secondary battery as a module for power source can be seriously damaged.